Basically the way the EU sees it, Google has a monopoly in a market: mobile operating systems. That is, if you're an OEM and you want to sell a device with an operating system, Google is currently the only place you can really turn. Apple exists but since it doesn't sell its operating system, it's not a participant in this market.

So the EU saw Google saying to OEMs "you can have Android but you have to install our stuff on it or pay extra" and decided that Google was using its monopoly position in one market (mobile OS) to give itself an advantage in other markets (app stores, browsers, search). They see this as anti-competitive.

As far as I know, Android is open source and any OEM is free to use it without asking permission. The licensing program is for the right to install proprietary Google apps like the Play Store or Google Maps. There are plenty of Chinese OEMs who aren't licensed and sell phones without the Play store.

Amazon tried to sell Android without Google Play, but the resulting Amazon Fire Phone didn't do very well. Unless Google is banned in your country like in China, no OEM wants to risk skipping out on Google Play.

Not necessarily -- trademark infringement requires an element of deception or confusion, not just any usage of the mark.

If an OEM sold a phone with a stock AOSP build, I think they'd be fine with calling it "Android" without permission. Google might attempt to enforce their mark anyway, but they wouldn't have much of a case.

If the phone ran a fork like LineageOS, the OEM would need to be more careful about their use of the mark, but I imagine they'd still be okay with language like "Android-based".

Google could do that, but it would hurt their business tremendously, as the amount of diverse brands which provide their own unique flavor on top of Android is what helps them keep this dominance.

Reducing the choice to just Google phones running Android will spark other providers to develop their own OS and increase competition in the market, which would indeed lead a great deal of people to say "Good job, EU" if the EU was the catalyst for such a scenario.

Google could shut it down and only publish their own phones, but they don't have the chops to become a premier customer goods maker. The field would be free for Apple until Samsung catches up. In the end Google lose negotiation power in getting their search engine, browser and services on Apple's and Samsung phones.

They're working on that, give it some time. The complaint from Spotify gets the ball rolling. The EU will do the rest. Two or three years from now they'll have a $4 billion fine for Apple.

"Spotify announced this morning that it’s filed an antitrust complaint against Apple with the European Union, alleging that the iPhone maker is harming consumer choice and stifling innovation via the rules it enforces on the App Store."

It's based on marketshare. iOS doesn't have enough marketshare on the smartphone market to be bothered by those laws. If apple was controlling the whole smartphone market, it could fall under those laws, even if its operating system wasn't open to other manufacturer.

Agreed, and this needs to stop in my opinion. The EU makes an enormous amount of money by suing tech-giants over and over again without doing enough research to know what companies in this sector are doing.

Those aren't based on nothing. There is laws and being a tech giant doesn't grant the right to go around those.
If those fines aren't justified, those companies can use the justice system in place to fight back, like everybody else.

It's not a free for all, get free money from tech companies with no legal background.